Aerial rockets and missiles which include folded, deployable guidance wings have been in use at least since the late 1940's, with the FEAR (Folding Fin Aerial Rocket) being used in the Korean and Vietnam conflicts, and the more recent Hydra 70 family of WAFAR (Wrap-Around Fin Aerial Rocket) and Advanced Precision Kill Weapon System (APKWS) laser guided missile. For many such weapons, the guidance wings are folded in a stowed configuration within the main fuselage until the weapon is launched, at which point the wings deploy outward through slots provided in the fuselage.
Typically, a rocket or missile is spun during its flight for increased accuracy and stability. For many missiles and rockets with folded, deployable guidance wings, the guidance wings are released from their folded and stowed configuration upon launch, and are deployed by the centrifugal force which results from the spinning of the weapon in flight. In some cases, the wing slots are covered by frangible seals which protect the interior of the missile from moisture and debris during storage, transport, and handling. In these cases the guidance wings must be deployed with sufficient initial force to enable them to penetrate the seals.
Clearly, wing deployment through frangible cover seals becomes more dependable as the initial deployment force is increased. However, there is a practical limit to how rapidly a missile can be spun. In one example, the average centrifugal force on the tip of a guidance wing at the beginning of deployment is only approximately 7.7 pounds at the minimum spin rate. This amount of centripetal energy may not be sufficient by itself to enable the wings to burst through the frangible slot covers. As a result, some weapons that include deployable folded guidance wings and frangible wing slot covers have demonstrated a tendency for the guidance system to fail due to a lack of proper guidance wing deployment. This problem can be addressed by a wing deployment initiator, which assists the deployment of the guidance wings by providing an initial burst of energy to help the wings break through the frangible covers.
In some designs, the wing deployment initiator uses explosives to push the wings through the frangible covers. However, this approach can be undesirable due to the violent forces produced by the explosives, and due to concerns about the safety and the long-term chemical stability of the explosives during storage of the weapon.
A torsion spring wing deploy initiator is described in co-pending patent application 61/322,461, filed Apr. 9, 2010, of which the inventors of the current invention are co-inventors. This approach avoids the problems of using explosives. However, the deploy assist mechanism of co-pending patent application 61/322,461 is somewhat bulky and complex, since it includes 65 machined hardware parts and 8 torsion springs. For certain applications, a more compact and less complex solution would be desirable, since the reduced complexity would lower the cost of production and would decrease the likelihood of failure if the mechanism did not perform as intended.
What is needed, therefore, is a mechanical wing deploy initiator with reduced bulk and reduced complexity in comparison to current designs and in comparison to co-pending application 61/322,461.